The invention concerns a power supply apparatus with identical individual power packs connected in parallel and decoupled from one another, with outputs for coupled output voltages, of which one is respectively adjusted by pulse duty control and the others are corrected by linear correction units.
Computer equipment or tower PCs with higher data processing power require power supply apparatuses with higher power. As a higher-power power supply apparatus, power supply apparatuses consisting of several identical individual power packs are used. The individual power packs are connected in parallel, decoupled from one another. They can be constructed in such a way that they produce coupled output voltages, of which one is adjusted by means of a pulse duty control and the others are adjusted by a linear correction. The linear correction is subject to a loss of power that is all the larger, the larger a derivative action has to be between an incoming voltage to be compensated and an outgoing compensated voltage.
Besides the higher power, additionally increased demands are placed on the fault tolerance of this power supply apparatus. A redundant power supply apparatus is required that continues to supply the computer in case of failure of an individual power pack, without failure or collapse of system voltages.
An additional demand on the power supply apparatus is that a failed individual power pack can be exchanged while the computer is running without voltage collapse. This measure is also known by the term "hot board replacement."
Finally, a uniform distribution of current to the individual power packs should be ensured.
It is known to control the uniform distribution of the current electronically. It is also known to use a separate power pack circuit for each output voltage. It is also known to decouple the outputs from the system voltage inputs of the computer with Schottky diodes, in order to obtain a redundancy given an output short circuit of a defective individual power pack. In addition, it is known to choose the number of individual power packs connected in parallel to be higher by one than the number actually required, in order to obtain in this way a power supply apparatus with redundancy in which defective individual power packs can be exchanged during operation.
The possibility is also known of connecting individual power packs with coupled output voltages in parallel. The output voltage with a highest output current is regulated for uniform current distribution via a pulse duty control. The coupled output(s) are regulated for a uniform current distribution by means of a transistor element as a controlling element in an output line. The regulation of the current distribution can thereby respectively ensue in an identical fashion: a central control block compares each output voltage separately with a target value. The deviation from this target value is amplified and is used as target current of the respective output. The actual current is acquired, is compared with the target value and is corrected correspondingly.
However, this method has the disadvantage that while the uniform current distribution of coupled individual power packs is indeed ensured, the losses due to this type of control are higher than is absolutely necessary. The reason for this is that an output voltage target value is used that is unalterably set, which value is not matched to the actually present output voltages. A power supply apparatus as described above is known from U.S. Pat. No. 5,038,265.
From DE 3 941 052 C1, a circuit arrangement for the parallel connection of power supply units is known, said units comprising a voltage regulation apparatus and a current regulation apparatus operating secondarily thereto, which respectively have identical resistance switching networks, as mean value formation units, between the voltage regulation apparatus and the current regulation apparatus, for the protection of a uniform load distribution to the power supply units connected together in parallel to form a power supply packet, which switching networks are connected with one another via at least one bidirectional control line and calculate a common mean value of a signal for all power supply units, which signal represents a measure for the output power to be emitted.
European reference 0 419 993, a power supply apparatus is known that consists of identical individual power packs decoupled from one another and connected in parallel, comprising outputs for coupled output voltages. With respect to each individual power pack, a pick-off circuit is provided for picking off a coupled output current, allocated to a controlling element within a power pack, as an electrical actual quantity, which circuit comprises among other things a drain connected with threshold switches. Overall, a uniform distribution of current to the individual power packs is effected by the formation of a target value from the mean value of the measured currents. However, the power packs comprise no coupled output voltages such that one is respectively adjusted by a pulse duty control and the others are corrected by linear correction units with a linearly controllable controlling element and a comparator connected with it. The present power supply apparatus thus does not solve the problem of ensuring a correction with minimal power loss and simultaneous uniform current distribution to the individual power packs connected in parallel in power supply apparatuses of this sort.
The aim of the invention is to ensure a correction of output voltages in a power supply apparatus of the type named above, with a minimal power loss and simultaneous uniform current distribution to the individual power packs connected in parallel.